b3f8815720
The _heal_instance_info_cache periodic task predates the introduction of the server external events API which is now the canonical way to refresh the cache. This change updates the default value of ``[compute]heal_instance_info_cache_interval`` to -1 disabling it by default. The nova-ovs-hybrid-plug job is extended to test the legacy configuration value and the config override is removed from nova-next Closes-Bug: #1996094 Related-Bug: #2089225 Change-Id: I33ac91bb4f3ead51af2f7005002d5eb5078540d9
43 lines
2.4 KiB
YAML
43 lines
2.4 KiB
YAML
---
|
|
upgrade:
|
|
- |
|
|
``[compute]heal_instance_info_cache_interval`` now defaults to -1.
|
|
|
|
In the early days of Nova, all networking was internal, then ``quantum``,
|
|
now known as ``neutron`` was introduced.
|
|
When the networking subsystem was being externalized and neutron was
|
|
optional Nova still needed to keep track of the ports associated with an
|
|
instance.
|
|
To that end, to avoid these expensive calls to an optional service the
|
|
instance info cache was extended to include network information and a
|
|
periodic task was introduced to update it in
|
|
``08fa534a0d28fa1be48aef927584161becb936c7`` as part of the
|
|
``Essex`` release.
|
|
|
|
As we have learned over the years per compute periodic tasks that call
|
|
other services do not scale well as the number of compute nodes increases.
|
|
In ``ce936ea5f3ae0b4d3b816a7fe42d5f0100b20fca`` the os-server-external-events
|
|
API was introduced. The server external events API allows external systems
|
|
such as Neutron to trigger cache refreshes on demand, this was part
|
|
of the Icehouse release. With the introduction of this API, neutron was
|
|
modified to send network-changed events on a per-port basis as API actions
|
|
are performed on neutron ports. When that was introduced the default value
|
|
of ``[compute]heal_instance_info_cache_interval`` was not changed
|
|
to ensure there was no upgrade impact.
|
|
|
|
In``ba44c155ce1dcefede9741722a0525820d6da2b8`` as part of bug #1751923
|
|
the _heal_instance_info_cache periodic task was modified to pass a
|
|
"force_refresh" forcing Nova to lookup the current state of all ports for
|
|
the instance from neutron and fully rebuild the info_cache. This has the
|
|
side effect of making the already poor scaling of this optional periodic
|
|
task even worse.
|
|
|
|
In this release, the default behaviour of Nova has been changed to
|
|
disable the periodic, optimizing for performance, scale, power consumption
|
|
and typical deployment topologies, where the instance network information
|
|
is updated by neutron via the external event API as ports are modified.
|
|
This should significantly reduce the background neutron API load in
|
|
medium to large clouds. If you have a neutron backend that does not
|
|
reliably send network-changed event notifications to Nova you can
|
|
re-enable this periodic task by setting
|
|
``[compute]heal_instance_info_cache_interval`` to a value greater than 0. |